Objective: Adenoid cystic carcinoma (ACC) of the head and neck grows slowly with structural differentiation, however, this tumor nevertheless also shows a highly invasive potential and a high recurrence rate. Extracellular matrices have been suggested to play an important role in the differentiation and growth of ACC. The aim of this study is to understand the roles of laminin 5 basement membrane (BM) components, including collagen IV and laminin γ2 for the high degree of invasiveness and the recurrence of ACC. Methods: Collagen IV and laminin γ2 were immunohistochemically localized in tissue sections from nine patients with ACCs. Results: Cribriform structures with pseudocysts were preserved in small invading tumor nests, and the expression of both of collagen IV and laminin γ2 was observed in the inner border of the pseudocysts and the surrounding area of the tumor nests. In areas of perineural invasion, the BM components continued to be expressed around the long tumor nests. Recurrent tumors consisted of multiple small nests with a few tumor cell layers, and the expression of the BM components was observed on both the inside of the inner tumor cells and the outside of the outer tumor cells, which was an obviously different appearance from that of the primary tumor. Conclusion: ACC appears to possibly grow and invade using the laminin 5 BM matrices while also preserving their differentiated architecture. The laminin 5 BM matrices might play an important role not only in the differentiation and growth, but also in the invasion and recurrence of ACC of the head and neck.
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